This invention relates in general to electronically-controlled vehicular brake systems, and in particular is concerned with a compensator assembly mounted in a hydraulic control unit to accommodate travel of a master cylinder piston.
Electronically-controlled hydraulic brake systems for vehicles are well known. Such systems typically include a hydraulic control unit (HCU) hydraulically connected between a master cylinder and wheel brakes. The master cylinder generates hydraulic forces in the brake circuit by pressurizing brake fluid when the driver steps on the brake pedal. A piston in the master cylinder travels in response to the brake pedal. The pressurized fluid travels through the fluid conduit in the circuit to actuate brake cylinders at the wheel brakes and slow the vehicle.
The hydraulic control unit contains control valves and other components such as a pump. Through an electronic controller, the control valves and other components selectively control pressure to the wheel brake assemblies to provide a desired braking response of the vehicle, such as anti-lock braking, traction control, and vehicle stability control.
The master cylinder includes a piston having at least one annular seal. Preferably, this seal is formed as a one-way seal commonly known as a lip seal. During a braking event, this seal can rest adjacent a comp port of the master cylinder. Fluid from the comp port tends to flap the seal back and forth, which can result in deterioration of the seal and premature failure. Known braking systems can provide additional displacement of the master cylinder piston to move the seal away from the comp port, but such systems add extra pedal stroke to every braking event, i.e., normal (base) braking as well as anti-lock braking. Additional pedal stroke is generally not desired in many braking systems.